In LTE (Long Term Evolution) standardized in 3GPP (3rd Generation Partnership Project) which is a group aiming to standardize a mobile communication system, an SON (Self-Organizing Network) technology, in which a base station autonomously adjusts a parameter according to a base station without using any manpower, is applied (refer to Non Patent Literature 1).
As one of the SON technology, in order to balance loads between base stations, there has been proposed technique of adjusting a base station parameter (specifically, a handover parameter) for determining a coverage on the basis of load information transmitted/received between neighboring base stations. Such an optimization technology is called MLB (Mobility Load Balancing), and is able to improve service quality provided to a radio terminal. In addition, the coverage indicates the range of a logical or physical communication area of a base station.
Specifically, in LTE, the following four types of load information have been defined (refer to Non Patent Literature 2): (a) the number of used PRBs (Physical Resource Blocks) each of which is an assignment unit of a time and frequency resource, (b) a load of a backhaul between a base station and a core network, (c) a hardware load of a base station, and (d) a ratio of available communication capacity to a capacity class that is an index indicating relative communication capacity of a base station.
In the aforementioned MLB, for example, if a base station detects that a load of a neighboring base station is lower than that of the self base station on the basis of load information from the neighboring base station, the base station adjusts a parameter such that the coverage of the self base station is reduced with respect to the neighboring base station. In this way, it is possible to increase the load of the neighboring base station while reducing the load of the self base station, resulting in the balancing of the loads.
Furthermore, for example, if is the base station detects that the load of the neighboring base station is higher than that of the self base station on the basis of the load information from the neighboring base station, the base station adjusts a parameter such that the coverage of the self base station is expanded with respect to the neighboring base station. In this way, it is possible to reduce the load of the neighboring base station while increasing the load of the self base station, resulting in the balancing of the loads.